Over consumption of alcohol can permanently damage the liver, kidney and brain. Damage to the nervous tissue incurred during development can lead to fetal alcohol syndrome which is the main preventable form of mental retardation. Although ethanol is widely understood to penetrate these organs and the placenta by diffusing through the lipid bilayer of cell membranes, it is unclear how ethanol penetrates certain tissues more easily than others. It is also unknown what confers these tissues increased permeability to ethanol and whether this can be dynamically altered to prevent damage. We are taking advantage of the powerful genetics of the model nematode C. elegans to provide insight into the molecular basis of alcohol permeability in vivo. This model organism has been used to discover genes involved in fundamental physiological processes including how alcohol elicits intoxication through conserved molecular targets. Previously, we and others have found that C. elegans requires an unusually high concentration of exogenous ethanol (500-1000 mM) to produce intoxication and to raise the internal tissue concentration to a level relevant to human consumption (20-50 mM). We have now discovered that although C. elegans shows this extraordinary resistance to exogenous ethanol when tested in low osmolarity conditions (150 mOsm), the animal reverts to human-like sensitivity to ethanol when tested in higher (physiological) osmolarity conditions (320 mOsm). Moreover, we find that short-term incubation of C. elegans at physiological osmolarity confers human-like sensitivity to alcohol in low osmolarity conditions. We hypothesize that specific conserved molecules allow rapid permeation of ethanol into the tissue of the animal, and these molecules can be dynamically altered to change permeability. To determine the molecular basis for this dynamic permeability to ethanol we propose three specific aims: 1) Test whether mutation of genes in different permeation pathways reduce behavioral responses to ethanol and tissue permeability to ethanol in C. elegans. 2) Discover whether these molecules are dynamically reorganized with chronic exposure to ethanol and/or osmolarity. 3) Determine whether these molecules alter permeation to ethanol in a heterologous system. Identification of the molecules that mediate alcohol permeability in the worm would first show that C. elegans has comparable sensitivity to humans and therefore strengthen its rationale as a model for human alcohol abuse, and second, provide attractive drug targets to prevent tissue damage following binge drinking in humans. PUBLIC HEALTH RELEVANCE: Identification of the molecules that mediate dynamic alcohol permeability in C. elegans is important to human health for two main reasons. First, it would first show that this powerful model invertebrate has equivalent sensitivity to humans, and therefore strengthen rationale for using C. elegans as a model for studying the effects of human alcohol abuse. Second, this would provide attractive drug targets to prevent tissue damage by alcohol after binge drinking in humans.